My gi dr found a 6mm nodule during my colonoscopy. what could this be?

Depends on pathology: Unless there is a pathologist on site, the polyps undergo a process of fixation, staining, sectioning, and interpretation. Most experienced gastroenterologists can however guess with about 90% accuracy whether a biopsied/removed polyp/nodule/mass/tumor has an appearance c/w cancer, & what further intervention for it may be needed. You should have biopsy results soon.

Ask: Ask your GI doctor, the practitioner who actually visualized the "nodule."